1. Field of the Invention
The present invention relates to firearms and in particular to an automatic machine pistol using gas discharge for recoil buffering and the silencer for the same.
2. Description of the Prior Art
Fully automatic or semi-automatic machine pistols are well known in the art. The use of gas pressure in automatic firearms to retard blowback action or to retard bolt blowback is also generally known. Examples of such gas retardation can be found in Irwin, "Gas Locked Firearm," U.S. Pat. No. 3,990,346 (1976) and Destree, "Firearm," U.S. Pat. No. 1,834,021 (1931). In Irwin, gas which is present in a locking chamber 24, as best depicted in FIG. 2, acts as a buffer to retard the blowback action and to prevent the bolt from slamming in a fully recoiled position. Vent 17, which initially had been closed with the bolt in the forward position by crosspin 13, is exposed and allows the remaining gas to vent slowly into chamber 26 as the bolt comes to rest at the end of its cycle. Port 18 in arm 3 communicates with chamber port 26 to vent remaining gases to the atmosphere. The barrel is provided with a gas port 8 which communicates with the barrel interior and locking chamber 7 depicted in FIG. 1. Port 8 is preferably located immediately forward of the cartridge. The close proximity of port 8 to the cartridge or firing chamber provides for entry of gas from the fired cartridge through port 8 into gas locking chamber 7 as soon as possible. After firing the cartridge, the bolt will tend to be forced rearwardly by the cartridge case thereby opening the breech.
However, there is sufficient delay of rearward movement to the bolt due to its weight as well as due to recoil spring 12 that the bolt does not begin to move rearwardly until the bullet has cleared gas port 8. Gas from the exploded cartridge charge enters locking chamber 7 against surface of plate 4. This high pressure gas urges plate 4 into a forward position and thus arm 3 maintains bolt 1 in a locked forward position until the projectile has left the muzzle and allowed the gas pressure to drop.
When the gas pressure in the barrel of the locking chamber has decreased sufficiently, the rearward momentum of the cartridge case against the forward bolt surface causes the bolt to be driven rearwardly. As the bolt nears its rearward position as shown in FIG. 2, plate 4 passes over and closes port 8 trapping and compressing the remaining gas in rear portion 24 of the gas locking chamber to cushion the movement of the bolt as it reaches the end of its rearward travel. Thus, gas present in locking chamber 24 acts as a buffer or air valve to retard blowback action and to prevent the bolt from slamming into its fully recoiled position.
However, in Irwin, discharge gas from the fired cartridge which has thus been used to retard blowback is then exhausted to the atmosphere through the gun casing generally, namely through any one of the many apertures, seams or openings which may be in communication directly or indirectly with gas locking chamber 24. This discharged gas is heavily laden with carbon, unburnt powder, and other small particles or products from the powder detonation. While some of these particles do escape with escaping gas to the environment, a significant fraction of them are deposited on any of the surfaces within the gun with which the discharge gas comes in contact. While such powder residue from a single shot is not excessive, the buildup of residue over a plurality of fired cartridges becomes excessive, particularly when the cartridges are rapidly fired as in an automatic weapon.
One of the persistent and unsolvable problems faced by small compact machine pistols has been due to fouling caused by excessive residue buildup which ultimately interferes with or jams operation of the gun. The resulting propensity of such machine pistols to become jammed has generally made them unreliable and unacceptable for military or police applications.
Therefore, what is needed is a simple, compact design for an automatic machine pistol which is not subject to the defects of the prior art as discussed above.